The present invention relates generally to a specially formed fabric having differential densities, and more particularly to a fabric that is specially designed in a manner that permits it to be readily formed into expandable honeycomb panels that can be utilized to provide practical, aesthetically pleasing decorative window coverings.
Colson U.S. Pat. No. 4,450,027 discloses a method and apparatus for forming expandable honeycomb insulation panels from thin film plastic material, whereby the panels have desirable energy conservation characteristics by virtue of their insulating and heat collective properties, as well as being aesthetically pleasing when used as window coverings. Briefly summarized, such patent discloses the concept of continuously creasing and folding strips of thin plastic film into an open sided tubular structure, then heat setting the folds in the film, and applying liquid adhesive to the portions of the film to be joined together to form the expandable honeycomb configuration.
Efforts have also been made to form expandable honeycomb panels from textile fabric materials rather than plastic to enhance the aesthetic appeal of the panels while sacrificing to some extent the energy conservation function of the panels. In attempting to form these panels from conventional thin fabric materials, a significant problem has been presented in terms of using a liquid adhesive to join the fabric to itself to provide the desired expandable honeycomb configuration.
When a textile fabric is used to make these panels, it must be quite sheer to provide the desired aesthetic and functional qualities normally associated with conventional sheer curtains and the like, but the open-mesh characteristic of this type of sheer fabric makes it virtually impossible to apply a liquid adhesive to the fabric solely at the required points of fabric juncture without also having the adhesive flow through the open-mesh sheer fabric to join other parts of the fabric to itself in a manner that will prevent proper expansion of the plurality of the individual honeycomb segments that make up the entire window panel. More specifically, when the individual segments are properly folded for ultimate expansion and contraction, the end portion of each such folded segment must be adhesively joined only to the center portion of the next adjacent segment, without any adhesive seeping through this point of juncture to cause adhesion at the end portions of an individual segment to the center portion of the same segment, which would prevent the necessary expansion of the individual segment when the final panel is used as a window covering. However, because of the aforesaid open-mesh construction of conventional sheer fabric, it is virtually impossible to prevent this seepage of adhesive during production of panels in high volume, commercially feasible manufacturing equipment.
In accordance with the present invention, a specially designed differential density fabric is provided which overcomes the above-described practical drawbacks of using a sheer textile fabric to form an expandable honeycomb window panel.